P: I would like to select images via full screen preview rather than multiple thumbnails

Thanks Jim, yes I noticed this has been available for IOS for around 6years now, but sadly not for us Android users of Lightroom Mobile. 

While waiting for your feature request to be considered, have you looked to see if there are size options for the thumbnails? On the iOS version of LrM there are 4 different size options for viewing the thumbnails on the import screen: tiny, small, normal, large. The large option can be as few as just two thumbnails on screen at a time, not quite as good as single image view but a lot better than the “very small” thumbnails that you are seeing. The options appear when tapping on the tri-dot menu at the top of the import screen.